diff --git a/src/components/ShareButton.tsx b/src/components/ShareButton.tsx
index 5a5d648..d0d7a66 100644
--- a/src/components/ShareButton.tsx
+++ b/src/components/ShareButton.tsx
@@ -4,7 +4,7 @@ import { QRCodeSVG } from 'qrcode.react';
 import { Button } from '@/components/ui/button';
 import { Dialog, DialogContent, DialogHeader, DialogTitle } from '@/components/ui/dialog';
 import { startBroadcast, type BroadcasterHandle } from '@/lib/webrtc/broadcaster';
-import { getBroadcastSource } from '@/lib/webrtc/broadcastSource';
+import { getBroadcastSource, onBroadcastSourceChange } from '@/lib/webrtc/broadcastSource';
 import { toast } from 'sonner';
 
 interface ShareButtonProps {
@@ -91,6 +91,24 @@ export function ShareButton({ variant = 'default', autoOpen, onHandleChange, onV
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [handle]);
 
+  // When the XR mirror canvas appears/changes (entering or exiting AR), swap the
+  // outgoing video track so viewers see the opaque mirror instead of the transparent main canvas.
+  useEffect(() => {
+    if (!handle) return;
+    const swapTo = (canvas: HTMLCanvasElement | null) => {
+      if (!canvas || typeof canvas.captureStream !== 'function') return;
+      const newStream = canvas.captureStream(24);
+      const oldStream = streamRef.current;
+      streamRef.current = newStream;
+      handle.replaceVideoTrack(newStream).catch((e) => console.warn('replaceVideoTrack', e));
+      if (oldStream) oldStream.getTracks().forEach((t) => t.stop());
+    };
+    // Apply current value immediately if mirror is already up
+    const current = getBroadcastSource();
+    if (current) swapTo(current);
+    return onBroadcastSourceChange(swapTo);
+  }, [handle]);
+
   // Cleanup on unmount
   useEffect(() => {
     return () => {
diff --git a/src/lib/webrtc/broadcastSource.ts b/src/lib/webrtc/broadcastSource.ts
index 163b2cd..5a15131 100644
--- a/src/lib/webrtc/broadcastSource.ts
+++ b/src/lib/webrtc/broadcastSource.ts
@@ -16,5 +16,5 @@ export function getBroadcastSource(): HTMLCanvasElement | null {
 
 export function onBroadcastSourceChange(cb: (c: HTMLCanvasElement | null) => void) {
   listeners.add(cb);
-  return () => listeners.delete(cb);
+  return () => { listeners.delete(cb); };
 }
diff --git a/src/lib/webrtc/broadcaster.ts b/src/lib/webrtc/broadcaster.ts
index fa4b7f6..10d5203 100644
--- a/src/lib/webrtc/broadcaster.ts
+++ b/src/lib/webrtc/broadcaster.ts
@@ -12,6 +12,8 @@ export interface BroadcasterHandle {
   code: string;
   stop: () => Promise<void>;
   onViewerCountChange: (cb: (n: number) => void) => () => void;
+  /** Swap the outgoing video track on every active peer (e.g. when the XR mirror canvas becomes available). */
+  replaceVideoTrack: (newStream: MediaStream) => Promise<void>;
 }
 
 const MAX_VIEWERS = 5;
@@ -32,6 +34,7 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
   const notify = () => listeners.forEach((cb) => cb(peers.size));
 
   let channel: RealtimeChannel | null = null;
+  let activeStream: MediaStream = stream;
 
   const handleMessage = async (msg: SignalMessage) => {
     if (msg.type === 'viewer-join') {
@@ -39,7 +42,7 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
       const pc = new RTCPeerConnection({ iceServers: ICE_SERVERS });
       peers.set(msg.viewerId, pc);
 
-      stream.getTracks().forEach((t) => pc.addTrack(t, stream));
+      activeStream.getTracks().forEach((t) => pc.addTrack(t, activeStream));
 
       pc.onicecandidate = (ev) => {
         if (ev.candidate && channel) {
@@ -96,9 +99,14 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
   channel = joinSignalingChannel(code, handleMessage);
 
   // Stop when the underlying stream ends
-  stream.getTracks().forEach((t) => {
-    t.addEventListener('ended', () => stop());
-  });
+  const attachEndedListeners = (s: MediaStream) => {
+    s.getTracks().forEach((t) => {
+      t.addEventListener('ended', () => {
+        if (s === activeStream) stop();
+      });
+    });
+  };
+  attachEndedListeners(stream);
 
   let stopped = false;
   const stop = async () => {
@@ -111,9 +119,27 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
     await supabase.from('share_rooms').update({ is_active: false, viewer_count: 0 }).eq('code', code);
   };
 
+  const replaceVideoTrack = async (newStream: MediaStream) => {
+    const newVideo = newStream.getVideoTracks()[0];
+    if (!newVideo) return;
+    activeStream = newStream;
+    attachEndedListeners(newStream);
+    for (const pc of peers.values()) {
+      const sender = pc.getSenders().find((s) => s.track && s.track.kind === 'video');
+      if (sender) {
+        try {
+          await sender.replaceTrack(newVideo);
+        } catch (e) {
+          console.warn('[broadcaster] replaceTrack failed', e);
+        }
+      }
+    }
+  };
+
   return {
     code,
     stop,
+    replaceVideoTrack,
     onViewerCountChange: (cb) => {
       listeners.add(cb);
       cb(peers.size);